Analysis of inhibitory mechanisms on Ca^<2+>-dependent K^+ channel influenced by exposure to a time-varying strong magnetic field.

我们检测了以下两种磁场对培养细胞的影响：(A)在0.07和1.7T之间变化的磁场，时间间隔为3s.(B)极低频(800高斯，50赫兹)磁场.(1)ME(A)对HeLa细胞的影响：将正常的培养液换成高K的培养液，可激活对K~+的摄取，增加细胞内Ca~(2+)浓度。膜通透性的钙离子螯合剂和钙离子依赖性钾离子通道阻滞剂可降低钾离子的摄取。染毒可部分抑制细胞对药物敏感性钾的摄取，并可完全抑制高钾条件下细胞内钙离子浓度的升高。但加入钙离子载体不能恢复微球对钾摄取的抑制作用。(2)FT-IR光谱分析ELF MF(B)对HeLa细胞的影响：在1500-1700 cm；-1&gt；区域的光谱分析中，酰胺II模(1540 cm-1)的吸光度降低，约1600 cm；后一条带的吸光度增加，表明自由羧基的C=O对称振动增加。这些结果提示了细胞膜蛋白质结构和细胞表面电学性质的改变。(3)极低频磁场对牛肾上腺嗜铬细胞的影响：我们检测了时变磁场对缓激肽刺激的嗜铬细胞内钙离子一过性升高的影响。加入缓激肽可在几分钟内引起细胞内Ca~(2+)的升高，在无Ca~(2+)的培养液中，加入MF可完全抑制细胞内Ca~(2+)的升高。当最大磁感应强度大于1.4T时，抑制作用持续15天。这些结果表明，暴露抑制了细胞囊泡中钙的释放。

We tested the effects of exposure to following two magnetic fields (MF) on cultured cells.(a) A time-varying MF changing between 0.07 and 1.7 T at an interval of 3 sec.(b) Extremely-low-frequency (ELF) ME (800 gauss, 50 Hz).(1) Effects of ME (a) on HeLa cells :K^+ uptake was activated and the intracellular Ca^<2+> concentration was increased by replacement of normal medium to high K^+ medium. A membrane-permeable Ca^<2+> chelating agent and Ca^<2+>-dependent K^+ channel inhibitors were found to reduce the K^+ uptake. Exposure to the MF partly inhibited the drug-sensitive K^+ uptake and completely suppressed the increase in intracellular Ca^<2+> in the high K^+ medium. But the inhibition of K^+ uptake by the MF was not restored by addition of Ca^<2+> ionophore. The suppression of K^+ fluxes could relate to a change in electric properties of cell surface and an inhibition of Ca^<2+> influx or Ca^<2+> release from cellular Ca^<2+> stores.(2) Analysis of ELF MF(b) effects on HeLa cells by FT-IR spectra :In analysis of the spectra of the 1500-1700 cm^<-1> region, absorbance of amide II mode (1540 cm-1)was decreased and a band about 1600 cm^<-1> was increased instantly by the MF.Increase in absorbance of the latter band reveals the increase on C=O symmetric vibration of free carboxyl. This results suggest changes in the protein structure of cell membrane and electric properties of cell surface.(3) Effects of ELF MF(a) on bovine adrenal chromaffin cells :We tested the effects of exposure to the time-varying MF(a) on transient increase in intracellular Ca^<2+> stimulated by bradykinin in chromaffin cells. Addition of bradykinin induced the increase in intracellular Ca^<2+> within few minutes.The exposure to the MF perfectly suppressed thc increase in cellular Ca^<2+> in Ca^<2+>-free medium. The inhibition occurred for 15 rain when the maximum magnetic flux density was more than 1.4 T.These results suggest that the exposure inhibits Ca^<2+> release from cellular vesicles.